1. Field of the Invention
The invention relates to a liquid crystal device using a chiral smectic liquid crystal having ferroelectricity.
2. Related Background Art
A liquid crystal device having bistability has been proposed by Clark and Lagerwall (specification of U.S. Pat. No. 4,367,924 and the like). As a liquid crystal having bistability, a ferroelectric liquid crystal having a chiral smectic C phase (SmC*) or H phase (SmH*) is generally used. The above liquid crystal has a bistable state comprising first and second optical stable states for an electric field. Therefore, different from an optical modulating device used in a conventional TN type liquid crystal, for instance, the liquid crystal is oriented in the first optical stable state for one of the electric field vectors and the liquid crystal is oriented in the second optical stable state for the other electric field vector. The above type of liquid crystal has a feature such that it extremely quickly has either one of the two stable states in response to the electric field which is applied and maintains such a state when no electric field is applied. By using such a feature, a problem such that the conventional TN type device has wrong characteristics about the angle of field is fairly essentially improved.
Particularly, as chiral smectic liquid crystal devices, there have conventionally been known devices as disclosed in, for instance, U.S. Pat. Nos. 4,639,089, 4,681,404, 4,682,858, 4,709,994, 4,712,872, 4,712,873, 4,712,874, 4,712,875, 4,721,367, 4,728,176, 4,740,060, 4,744,639, 4,747,671, 4,763,992, 4,773,738, 4,776,676, 4,778,259, 4,783,148, 4,796,979, 4,800,382, 4,802,740, 4,818,075, 4,818,078, 4,820,026, 4,836,656, 4,844,590, 4,869,577, 4,878,740, 4,879,059, 4,898,456, 4,907,859, 4,917,471, 4,932,757, 4,932,758, 5,000,545, 5,007,716, 5,013,137, 5,026,144, 5,054,890, and 5,078,475, and the like.
When a chiral smectic liquid crystal is injected to a liquid crystal panel of a large area (for instance, a diagonal size is equal to or larger than 14 inches) and a cell is formed, zigzag defects as disclosed in, for instance, U.S. Pat. No. 4,932,758 occur. It has been found out that such an occurrence tendency of the zigzag defects delicately relates to an anchoring effect to the substrate surface on which the liquid crystal molecules are oriented.